What is fstab?

Answer 1

The file /etc/fstab is commonly found in UNIX (Such as BSD, UnixWare, or OS X) systems or UNIX-like systems (Such as Linux, Plan 9, or Minix.).

It is a plaintext file, not always modified by the user, and it stands for FileSystem TABle.

Though it can describe every filesystem on your computer, it is usually just used to describe filesystems that need to be mounted at boot as opposed to everything available.

Typically you'll find:

A description of your root filesystem, which is the topmost level all directories and mounted filesystems will branch off of.

A description of your pseudoterminal and shared memory virtual filesystems which are usually required in Linux by most applications (Your terminal emulators and the screen command depend on pseudoterminal devices to work.)

A description of your swap partition, where virtual memory or hibernation data will be stored. This particular filesystem is not actually mounted, but activated and given over to the control of the *nix memory manager. There is no way to explore this filesystem as a user.

Other filesystems and mountpoints may also be commonly described, the three most common being /home, /usr, and /boot.

Removable media can also be described in here, but it's impractical and inflexible, not to mention grossly unnecessary due to HAL and udev, which will manage such things in much the same way as Windows manages its removable media. That is beyond the scope of this answer.

Long answer short, it's a configuration file Linux needs to boot and function properly, don't mess with it unless you know what you are doing. Your Linux distribution's installer is likely to automagically generate this file for you.

Answer 2

/etc/fstab is a file that defines mountpoints for your storage devices on startup/boot.

This also includes the system partitions that your Linux distribution requires to start and run.

Each mountpoint in your fstab can be defined by [PART]UUID, or by the format /dev/sdXY. (where X is the letter of the Nth storage device, and Y is the partition number), the filesystem, mount point (location), and some filesystem-specific options (e.g. read-write/read-only)

Answer 3

The fstab file is a list of file systems to be automatically mounted when the system boots up.